1. Field of the Invention
The present invention relates to a waveform control type laser processing apparatus.
2. Description of the Related Arts
In a laser processing apparatus which imparts pulse laser beams onto a workpiece to perform laser processing such as welding or cutting, use has hitherto been made of a technique for variably controlling a waveform of a laser power of the pulse laser beams or a waveform of a predetermined electrical parameter corresponding thereto, so as to be able to deal with various processing demands.
In the case of such a waveform control system, a desired reference waveform for waveform control is previously set and entered into the laser processing apparatus. The laser processing apparatus comprises a laser oscillation unit which oscillates and outputs laser beams in response to a supply of electric power from a laser power supply unit, and a laser control which provides a control of the laser power supply unit in an open loop control system or a closed loop (feedback) control system in such a manner as to allow a change with respect to time, i.e., a waveform of a laser power of the laser beams oscillated and output from the laser oscillation unit or a waveform of a predetermined electrical parameter of the laser power supply unit to conform to the reference waveform.
Reference is made to FIGS. 21 to 23 to describe a typical method of setting the reference waveform in the conventional laser processing apparatus of this type.
The conventional apparatus has a setting mode screen as shown in FIG. 21 on which a plurality of, e.g., three flash periods FLASH1, FLASH2, FLASH3 and two cooling periods COOL1, COOL2 are prepared as waveform element items for defining a reference waveform for a single pulse laser beam.
Desired time within a predetermined range (e.g., 0 to 20 ms) is set and entered into the flash periods FLASH, with a selection of the laser power value from one of two different modes [A, B]. Herein the laser power value modes [A, B] are represented as set voltages within the laser power supply unit corresponding to the laser power and are set to desired voltage values in the separate setting items on the same setting mode screen. In the shown example, setting is made of A=300V and B=500V. Time within a predetermined range (e.g., 0 to 20 ms) is only set and entered into the cooling periods COOL.
FIG. 22 illustrates a wave form pattern of the reference waveform corresponding to the set value of FIG. 21. FIGS. 23A to 23D illustrates other examples of the reference waveform pattern. Ordinary applications often employ a single pulse waveform by continuously connecting a plurality of flash periods FLASH without inserting any cooling periods COOL as in the examples of FIGS. 23A-D.
It is to be noted in FIG. 21 that for easier illustration dotted lines encloses items which can be set and entered on the setting screen mode. No description is given to items having no direct relation to the setting of the reference waveform.
In the conventional laser processing apparatus, as set forth hereinabove, the user (operator) previously sets desired values of a plurality of different laser power value modes [A, B] to allocate either one of the laser power value modes to each flash period, thereby setting the reference waveform for laser power waveform control.
In the case of such a setting system, if the number of the laser power value modes is small, for example, two [A, B], the type of the reference waveform pattern which can be set is also limited, making it difficult to deal with a diversity of workpieces.
An increase in the number of the laser power value modes to solve this problem will in turn result in complicated setting entry operations, adding to the burden of the user side.
In particular the same or similar reference waveform pattern is often selected for workpieces of the same material, although a change of thickness of the workpieces needs a change of laser power value in spite of the same material. For example, increase of the thickness results in increase of the laser power value.
In this respect, to increase by e.g., 15% in total the laser power value of the reference waveform with the same waveform pattern, the above conventional laser processing apparatus requires the user to figure out by himself/herself a 15% increase value (new set value) for each of the laser power value modes [A, B] and to enter the thus obtained new set value on the setting mode screen (FIG. 21). This results in troublesome operation even in the case of a change of a single laser power value mode.
As described above, however, an increase in the number of the laser power value modes to add to the degree of freedom of the reference waveform pattern brings about a further increase in the inconvenience of the user operation.
In addition the conventional laser processing apparatus did not display any waveform pattern of the thus set reference waveform on the screen, so that the user had to imagine an ideal waveform diagram in his/her mind from the set values of the waveform element items or alternatively, the user had to actually draw a waveform diagram on paper, which was a cause of more time taker to set of alter the reference waveform.
Furthermore, it was inconveniently impossible to adjust at will the heating rate or cooling rate in the laser processing since the leading edge and the trailing edge of the reference waveform were set only perpendicularly with no inclination.
The present invention was conceived in view of the above problems involved in the prior art. It is therefore an object of the present invention to provide a laser processing apparatus capable of setting a reference waveform for waveform control of a laser output or an electrical parameter corresponding thereto, in the form of a diversity of waveform patterns, through a simple user operation.
Another object of the present invention is to provide a laser processing apparatus allowing an easy and free alteration of the once set reference waveform for waveform control.
A further object of the present invention is to provide a laser processing apparatus enabling the rise/fall of a laser output waveform to be set to arbitrary waveforms and ensuring any desired adjustment of the heating rate or cooling rate in the laser processing.
In order to achieve the above objects, according to an aspect of the present invention, there is provided a laser processing apparatus comprising laser oscillation means for oscillating and outputting pulse laser beams; laser power supply means for supplying an electric power for laser oscillation to the laser oscillation means; and reference value setting means for setting reference values for laser outputs of the pulse laser beams or for electrical parameters of the laser power supply means corresponding thereto. The laser processing apparatus also comprising waveform section setting means for setting, as values of ratio relative to the reference values, laser output values or electrical parameter values of a plurality of waveform sections for constituting a reference waveform used for the waveform control for the laser outputs of the pulse laser beams and the electric parameters; reference waveform generation means for generating waveform data representative of the reference waveform on the basis of reference values which have been set by the reference value setting means and of ratios relative to the reference values of waveform sections which have been set by the waveform section setting means; and waveform control means for providing a control of the laser power supply means in such a manner that the laser outputs of the pulse laser beams or the electric parameters conform to the reference waveform imparted by the reference waveform generation means.
In the laser processing apparatus the reference waveform generation means preferably include upslope generation means for acquiring an upslope waveform section of the reference waveform from time of the first period among the plurality of periods and from time and a laser output ratio or an electrical parameter ratio of the second period and from the reference value.
In the laser processing apparatus the reference waveform generation means may include downslope generation means for acquiring a downslope waveform section of the reference waveform from time and a laser output ratio or an electrical parameter ratio of the second last period among the plurality of periods and from the reference value and from time of the last period.
Preferably the laser processing apparatus further comprises set value display means for displaying the reference value and set values of the time, laser output ratio or electrical parameter ratio of the period.
Preferably the laser processing apparatus further comprises reference waveform graph display means for displaying a reference waveform graph representative of a waveform pattern of the reference waveform.
In the laser processing apparatus the reference waveform graph display means may acquire the reference waveform graph on the basis of times of a plurality of periods which have been set by the pulse period setting means, and of a laser output ratio or an electrical parameter ratio of each period which has been set by the ratio setting means.
In the laser processing apparatus the waveform section setting means may include pass point time setting means for setting times of a plurality of pass points on a waveform of the reference waveform, and ratio setting means for setting a laser output value or an electrical parameter value of each of the pass points in the form of a value of ratio relative to the reference value.
In the laser processing apparatus the reference waveform generation means preferably include upslope generation means for acquiring an upslope waveform section of the reference waveform from time and a laser output ratio or an electrical parameter ratio of the first point among the plurality of pass points and from the reference value.
In the laser processing apparatus the reference waveform generation means preferably include downslope generation means for acquiring a downslope waveform section of the reference waveform from time and a laser output ratio or an electrical parameter ratio of the second last point among the plurality of pass points and from time of the last point and from the reference value.
Preferably the laser processing apparatus further comprises set value display means for displaying the laser output reference value and set values of the time, laser output ratio or electrical parameter ratio of the pass point.
Preferably the laser processing apparatus further comprises reference waveform graph display means for displaying a reference waveform graph representative of a waveform pattern of the reference waveform.
In the laser processing apparatus the reference waveform graph display means may acquire the reference waveform graph on the basis of times of a plurality of pass points which have been set by the pass point time setting means, and of a laser output ratio or an electrical parameter ratio of each point which has been set by the ratio setting means.
According to the laser processing apparatus of the present invention, appropriate reference values were set and entered for pulse laser beams or electrical parameters corresponding thereto, with setting entry, as ratios relative to those reference values, of the laser output values or the electrical parameter values in a plurality of waveform sections for constituting the laser output waveform or the electrical parameter waveform, whereby a reference waveform for waveform control can be obtained on the basis of those reference values and laser output ratios or the electrical parameter ratios of the waveform sections.
Furthermore, a waveform pattern of the set reference waveform was allowed to appear in the form of a waveform graph on the screen. By virtue of this, it is possible to set the reference waveform for waveform control as a diversity of waveform patterns through simple user operations and to easily and freely alter the once provided reference waveform for waveform control.
It is further possible to set the rise/fall sections of the laser output waveform or the electrical parameter waveform to arbitrary waveforms, so that the heating rate or cooling rate in the laser processing can be adjusted at will.